Results 1 to 2 of 2

Math Help - integration of application

  1. #1
    Newbie
    Joined
    Apr 2007
    Posts
    5

    integration of application

    hey guys, im struggling with these 2 questions, think im getting brain freeze, must be missing something obvious. can any one help?

    1.the charge Q COloumbs on a capacitor varies with time according to the formula

    dQ/dt = -250sin100t

    find the charge after 0.0005 seconds if Q=0.015 coloumbs at time t=0 seconds?


    2. dQ/dt = 100cos200t

    find the charge after 0.0005 seconds if Q=1 coloumbs at time t=pie/400 seconds?


    and also, i know this is prob a stupid question but can someone tell me what

    exp 1 =?
    exp 0 =?
    exp -1=?

    thanks!!!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Mar 2008
    Posts
    148
    1. \frac{dQ}{dt} = -250\sin(100t) is a separable differential equation, which you can solve to get a formula for Q(t).

    Q = \int dQ = \int -250\sin(100t) dt = \frac{250}{100}\cos(100t) + C= 2.5 \cos(100t) + C.

    where C is some constant. To find this constant use the initial values given.

    0.015  = Q(0) = 2.5 \cos(0) + C \Rightarrow C = 0.015 - 2.5 = -2.485

    So the equation for Q(t) = 2.5 \cos(100t) -2.485. use this to find the charge at any time. Problem 2 is basically the same problem with different values.
    ___________________
    e^0 = 1 since any non-zero number to the 0 is 1.
    e^1 = e since any number to the first power is itself.
    e^{-1} = \frac{1}{e} \approx 0.367879441.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Application of Integration
    Posted in the Calculus Forum
    Replies: 4
    Last Post: July 27th 2011, 07:55 AM
  2. application of integration
    Posted in the Calculus Forum
    Replies: 4
    Last Post: February 17th 2010, 11:51 AM
  3. Application of Integration-Mean
    Posted in the Calculus Forum
    Replies: 2
    Last Post: July 2nd 2009, 02:46 AM
  4. Help in Application of integration.
    Posted in the Calculus Forum
    Replies: 6
    Last Post: May 19th 2009, 07:04 AM
  5. Help in Application of integration.
    Posted in the Calculus Forum
    Replies: 0
    Last Post: May 17th 2009, 03:55 PM

Search Tags


/mathhelpforum @mathhelpforum